A fish population in a pond changes at a rate of p′(t) fish per month, where t is measured in months. If ∫47p′(t)dt=−120, which of the following is the best interpretation of this value?
a) The population increased by 120 fish from month 4 to month 7.
b) The average rate of change of the population was −40 fish per month over the interval from month 4 to month 7.
c) The population decreased by 120 fish from month 4 to month 7.
d) The population decreased by 120 fish per month between months 4 and 7.